1. Field of the Invention
The invention relates to a three-dimensional multi-frequency antenna, and more particularly, to a three-dimensional multi-frequency antenna capable of being applied in various wireless communications networks.
2. Description of the Prior Art
An electronic product with wireless communications functions, such as a notebook computer, can utilize a built-in antenna to access wireless communications networks, which carry information by radio waves. With regard to different wireless communications systems, the operating frequencies are also different, for example, operating frequency bands of a wireless fidelity (Wi-Fi) network is about 2.4 GHz˜2.4835 GHz and 4.9 GHz˜5.875 GHz, an operating frequency band of a Bluetooth network is about 2.402 GHz˜2.480 GHz, operating frequency bands of a worldwide interoperability for microwave access (WiMAX) network is about 2.3 GHz˜2.69 GHz, 3.3 GHz˜3.8 GHz and 5.25 GHz˜5.85 GHz, an operating frequency band of a wideband code division multiple access (WCDMA) network is about 1850 MHz˜2025 MHz, an operating frequency band of a global system for mobile communications 1900 (GSM 1900) network is about 1850 MHz˜1990 MHz, and an operating frequency band of an international mobile telecommunications-2000 (IMT-2000) network is about 1920 MHz˜2170 MHz. Therefore, in order to help users more easily access various wireless communications networks, an ideal antenna should be able to cover operating frequency bands demanded by the above mentioned wireless communications networks. Furthermore, in order to cope with current ministration trends of portable electronic devices, like notebook computers, antenna sizes should be designed as small as possible.